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Destin Perry (Section 1)

The Physics of the AURORA BOREALIS.

The Aurora Borealis is a phenomena that has captivated many since the beginning of time, illuminating the skies of northernmost areas of earth. These whimsical lights used to cause a conundrum among students and professors alike, since recorded time. There has been several unsuccessful theories in history, Seneca, the roman philosopher, wrote the first recorded thought about them, writing that he ‘Oft wondered whether they were below or above the clouds.’ Since then, several other big names in the science world have given their thoughts on the matter. Ben Franklin wrote that, “The Mystery of the Northern Lights..” was caused by a concentration of electrical charges in polar regions, but intensified by snow and other moisture. In 1962, the “Leaky Bucket Theory” was disproved, which was a hypothesis that stated the Aurora was just radiation overflowing from the Radiation Belt, which is an area around a planet where charged magnetic particles gather. In the end, we’ve come to the correct conclusion, which was the solution to curious minds everywhere.

Auroras result from the emission of photons in Earth’s upper atmosphere above 80km (or 50 miles, for all those obsolete Americans out there!) from ionized nitrogen atoms regaining an electron, and oxygen and nitrogen atoms returning from an excited state, to a ground state. They become ionized and excited by solar winds and magnetospheric particles being funneled down and accelerated through the Earth’s magnetic field lines. When excited, the only thing they can do to return to their “ground state” is to emit a photon. When this photon is emitted, our eyes percieve it as light, and we have experienced the beautiful Aurora that has captivated curiousity since the captivation of curiousity onto recorded texts (Ha!).

In an Aurora, the photons emitted vary depending on the type of air molecule returning to ground state. For example, in an oxygen atom, the color we percieve is a green or brown-ish red, depending on the energy involved. In nitrogen return state, the color we percieve is a red, or a blue. Blue if the atom regains an electron after ionized, or Red if returning to ground state from excited state. Of course, this is where color, and how our eyes percieve it can make the issue a whole lot more complicated. For example, it takes about a third of a second for an excited oxygen molecule to emit green. But in some situations, if left for up to two minutes, the energy let off will be percieved as red. This means that the higher up the Borealis is occuring, the more chance you will be seeing the dark reds and browns, as the air pressure is much thinner, and the oxygen molecules have an easier time waiting for the time to discharge their red.

(Examples!)

http://upload.wikimedia.org/wikipedia/commons/thumb/6/63/Aurora_australis_panorama.jpg/800px-Aurora_australis_panorama.jpg

But wait! Where do all these photons come from? How do they just hit the earth and make beautiful phenomena for the world to enjoy??

The answer is solar storms. Solar storms emit from the Sun fairly actively. Sometimes, several a day will emit, sometimes, once a week. These solar storms fly through space so fast, that it only takes about 6 hours to get to mercury, and 15-18 hours to get to earth. When arriving at earth, these solar emissions hit the earths magnetic fields, creating the magnetic disturbance as described before.

Whether you are interested in the physics behind how our earth works, or you want to experience a beautiful natural occourence, the Aurora Borealis is an amazing spectacle that should be witnessed physically (Well, as physical as photons get) by everyone.

Thanks for reading.

And here’s a pretty video to watch!

http://www.theguardian.com/travel/video/2013/mar/25/northern-lights-footage-captured-in-iceland-video

Sources ::

http://physicscentral.com/explore/pictures/aurora-borealis.cfm

http://www.northernlightscentre.ca/northernlights.html

http://www.iop.org/education/higher_education/stem/showcasing/page_54368.html

http://webcache.googleusercontent.com/search?q=cache:cD4c1lE-TmsJ:www-spof.gsfc.nasa.gov/Education/aurora.htm+&cd=8&hl=en&ct=clnk&gl=us

Emil Der-Grigorian (Section 2)

Daniel Bernoulli was a Swiss physicist who is best known for his work in creating the principles that the led to the shape of the airplane wing.  His father was one of the early developers of calculus, his uncle was one of the first people to discover the theory of probability, and he, himself, discovered the Bernoulli Principle, which states that “the increase in the speed of fluid occurs simultaneously with a decrease in pressure” (a theory that is solely responsible for what we know today about the generation of lift.

Bernoulli’s principle states that an aircraft can achieve flight through the shape of its wing.  The shape allows the air to flow faster over the top, and slower underneath, which creates lower pressure on top and higher air pressure at the bottom. The higher pressure pushes the aircraft up through the lower pressure, thus creating lift. To get this pressure difference, Bernoulli came up with the aerofoil shape from observing birds and their wing shape.  He noticed that the shape allowed for the object to overcome weight.  By creating a rounded leading edge, he was able to reduce drag and further facilitate the flow of air over the wing. By applying Newton’s three laws, we now have the physics of flight.

A funny explanation of this can be heard from my dad every Christmas when my nephew asks him how Santa flies (and I am certain that about five minutes in, the poor kid regrets asking an aerospace engineer how Santa’s sleigh flies).  The explanation goes as follows:

“Santa needs to get the sleigh to go really fast so he can generate lift.  That’s when the pressure under the sleigh is lower than above the sleigh.  The reindeer’s antlers are VERY aerodynamic and reindeer run very fast.  So as they run, they generate thrust, which then leads to air flowing over the antlers.  The top pressure gets lower and the bottom of the antlers generates lift.  Their large feet are like paddles that kick to keep the sleigh moving while they are in the air and that’s how Santa’s sleigh stays in the sky.”

The Bernoulli Principle can also be applied to more than just aerodynamics.  His equation also proves that when a fluid flows through pipes of varying widths, energy is neither created nor destroyed.  The wider the pipe, the slower the flow, but in the more narrow parts, the flow (velocity) gets faster. Think of how when washing the car or watering the lawn, one can get a higher-pressure stream by placing their thumb on the tip of the hose and constricting the opening (or for example when a cleaner hose tip is placed on the end, how that increases the pressure of the spray).

Bernoulli has contributed to the creation of things we use in our everyday lives that we do not really give much thought to.  Simple things that we take for granted, these pioneers and great thinkers could not take for face value.  Without their contributions and analyses, who knows where we would be today with our understanding of space and simple phenomena that occur in our backyards.

http://www.portageinc.com/community/pp/flight.aspx

http://library.thinkquest.org/2819/bernoull.htm

http://www.portageinc.com/community/pp/flight.aspx

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